1. Field of the Invention
This invention relates to polyamides. In one aspect, the invention relates to a process for manufacturing polyamides from .alpha.,.omega.-diamine and an .alpha.,.omega.-diamide while in another aspect, the invention relates to a process utilizing an oxygenated phosphorus compound as a catalyst. In still another aspect, the invention relates to an improved process for manufacturing nylon-6,6 from hexamethylenediamine and adipamide utilizing a catalyst system composed of an oxygenated phosphorus compound.
2. Description of the Prior Art
It is known in the art that commercially available nylons may be prepared by polymerization of various monomers and combinations of monomers. For example, various nylons may be prepared from the polymerization of diamines with dicarboxylic acids, the polymerization of dinitriles with diamines in the presence of water, the polymerization of aminonitriles in the presence of water, or the polymerization of lactams.
In part, the instant invention deals with nylons resulting from the polymerization from diamines and diamides. Very few references suggest the polymerization of these two monomer types. For example, U.S. Pat. No. 3,900,450 teaches a process for polymerizing amino acids, diamines, dibasic carboxylic acids and other amide forming derivatives in which diamides are specifically included.
In part, the instant invention also relates to the use of an oxygenated phosphorus compound as a polymerization catalyst. Recently Hoffmann et al., U.S. Pat. No. 4,436,898 disclosed an improved method for preparing a high molecular weight polyamide from a dinitrile, diamine and water by conducting the polymerization in the presence of an oxygenated phosphorus compound, such as phosphoric acid, or an ammonium salt or an ammonium alkyl salt of the acid. Also recently, Coffey et al., U.S. Application Ser. No. 540,596, now U.S. Pat. No. 4,490,521, disclosed a method for the improvement of resin thermal stability through the use of metal salts of oxyphosphorus acids, such as disodium phosphite, as the catalyst.
Lastly, the instant invention relates to the production of nylon-6,6 from hexamethylenediamine and adipamide. Commercially nylon-6,6 is produced from hexamethylenediamine and adipic acid. The present invention offers an alternative to the adipic acid route in preparing this most useful polymer.